还是 is used in questions 或者 is used in affirmative sentences

或者this word means or,it offers choice.还是I think the suitable word to express it is" still ,had better"

或者 functions just like English "or". There is no equivalent of 还是 in English. It's a question word that translates into English as a question woth "or" in it. Ex. 你想喝水还是啤酒？ - "Do you want to drink water or beer?" 还是 makes this sentence a question. 我想喝水或者啤酒。 - I want to drink water or beer.

或者 could be exactly translated as 'or' in english while 还是 is more than that. because 或者 is more likely comparing two parallel choices, meanwhile 还是 bases on the 'no' implication to the former choice you offer. that's why although these two words can be interchanged in most of the occasion, still slightly different notice.

When you ask someone to pick one from two choices, use 还是: Are you a boy or a girl? Do you drink tea or coffee? When it's maybe one or the other or both or neither, use 或者: I'm going to Beijing or Shanghai next week. Today or tomorrow, we're going to meet up. When used with phrases like "I don't know...", use 还是: I don't know if this is his or hers? I'm not sure if he's coming this morning or this afternoon. 还是 has other meanings too like when used with 吧 for "had better": We're going to be out all day. We'd better take something to eat. He needs the money today. You'd better go to the bank. When there are two options, you can use 或者 before both (one for "either" and one for "or"): Either you ask him or I will. Stop waffling. Either tell me or shut up.